1. Technical Field
Embodiments of the inventions relate to memory systems in which a memory controller dynamically changes between a first mode in which the memory controller provides certain commands as separate single commands and a second mode in which the memory controller provides a consolidated command that represents the single commands.
2. Background Art
Various arrangements for memory devices in a memory system have been proposed. For example, in a typical synchronous dynamic random access memory (SDRAM) system, memory devices communicate data through bidirectional data buses and receive commands and addresses through command and addresses buses. The memory devices have stubs that connect to the buses in a multi-drop configuration (coupling three or more points). Other designs include point-to-point signaling (coupling two points). The point-to-point signaling may be unidirectional or bidirectional. The signaling may be single ended or differential. In some systems, address, command, and write data may be on the same conductors.
Memory controllers provide various commands to memory devices. These commands include an activate command (ACT), a precharge command (PRE), a read command (RD), and a write command (WR). Read and write commands are sometimes called CAS commands.
Memory modules include a substrate on which a number of memory devices are placed. The memory devices may be placed on only one side of the substrate or on both sides of the substrate. In some systems, a buffer is also placed on the substrate. For at least some signals, the buffer interfaces between the memory controller (or another buffer) and the memory devices on the module. In such a buffered system, the memory controller can use different signaling with the buffer than the buffer uses with the memory devices. A dual in-line memory module (DIMM) is an example of a memory module. Multiple modules may be in series and/or parallel. A system may include one or more than one memory channel.
Some computer systems having included some memory devices on a motherboard and other memory devices on a memory module or other card in a connector on the motherboard.
In some memory systems, the memory devices receive signals and repeat them to other memory devices as well as provide requested data signals to next memory devices. Read data signals can be provided to the memory controller through a point-to-point unidirectional return link from the last memory device in a series of memory devices in a looped fashion or from a memory device that is not the last memory device in the series.
Memory controllers have been used in chipset hubs and in a chip that includes a processor core. Some computer systems include wireless transmitter and receiver circuits.